This invention concerns an oil-sealed vane pump.
Such a pump basically comprises a stator consisting of a body comprising a cylindrical housing wherein a cylindrical rotor rotates eccentrically and tangentially to a generatrix of said housing. The rotor supports two diametrically opposed vanes applied by means of springs (as well as by centrifugal force) to the stator. A suction port and a discharge port respectively are provided on each side of the stator and rotor tangency generatrix. The discharge port is provided with a check valve. The seat of this valve consists of the bottom of a spot facing in the stator. The foregoing assembly is placed in an oil-filled tank. The suction port is connected to a tank inlet pipe and the discharge port leads to the inside of the tank which is itself provided with an outlet pipe.
Oil required for lubrication and sealing between the vanes and the stator as well as between the rotor and its line of tangency with the stator enters through an injection orifice in one of the side walls of the stator. This orifice is fitted with a cutoff valve made to alternately open and close in the course of pump operation by means of a rotary actuator mounted on the rotor shaft. This valve prevents oil entering the stator when the pump is stopped. However, in the event this actuator fails and the valve stays open when the pump is stopped, the stator fills with oil and on restarting the pump a large amount of oil is ejected through the discharge port. Since the flow passage between the valve, located at the discharge port , and the walls of the spot facing in which the valve is mounted is too small to allow such a large flow of oil to pass, such ejections result in damage to the valve and eventually to its spring, such as deformation or sticking.
The above-mentioned spot facing enables retention of a small amount of oil providing a seal between the valve and the stator when the pump is stopped.